Always sad when a cat goes missing.
A family who live near us sent a message around, to say that their cat had gone missing a while back, and asking everyone to keep an eye open. No news for a week or so, when we heard that he had suddenly reappeared, looking very sorry for himself and extremely thin. Nobody knows what happened but the best guess is that he got shut up in a shed somewhere nearby, had access to some source of drinking water and made a bid for freedom when the owner of the shed next opened it up.
...So they sometimes come back. We had a very elderly mog go missing, some years ago and, although I'm fairly certain that his time had come and that he just went to sleep somewhere, and never woke up, it's upsetting not to know for sure.